1. Field of the Invention This invention relates to improvements in a cylinder direct injection spark-ignition internal combustion engine, and more particularly to a control system for variably controlling the intensity of swirl to be generated in a cylinder of the engine.
2. Description of the Prior Art
Hitherto cylinder direct injection spark-ignition internal combustion engines have been proposed and put into practical use, in which fuel is directly injected into each cylinder of the engine. Typical one of them is disclosed in Japanese Patent Provisional Publication No. 2-125911. This engine is configured as follows: Each piston is formed at its crown with a cavity. A spark plug is installed to a cylinder head and located to face the peripheral portion of the cavity. A fuel injector is disposed to project in the cylinder so as to directly inject fuel into the cylinder, and located to prevent injected fuel from directly splashing onto the spark plug.
Additionally, this engine is provided with a device for controlling the intensity of swirl of air-fuel mixture to be generated in the cylinder. In a low engine load operating range, the intensity of swirl is increased by the swirl intensity controlling device, while fuel is injected from the fuel injector at the latter half of compression stroke, thereby gathering combustible mixture around the spark plug. The combustible mixture is burnt to accomplish stratified charge combustion in the cylinder. In a high engine load operating range, the intensity of swirl is decreased, while fuel is injected on intake stroke thereby to previously mix fuel and air. This forms homogeneous air-fuel mixture throughout the whole combustion chamber thus to accomplishing homogeneous charge combustion in the cylinder.